Adjustable Fuel Pressure Regulator for TBI equipped F-bodies

So far if you’ve been reading the ultimate TBI series you will have noticed that the TBI unit you have been dealing with is really quite simple and user freindly. Just when you thought your free mods of the TBI unit were over you now know that the factory fuel pressure regulator can be made adjustable, infact its adjustable from the factory. GM just does a really good job of hiding this. Turbo city actually markets an adjustable fuel pressure regulator for approx. $65 which is really nothing more than the factory unit with a large adjusting screw! Thus I felt it neccessary to show my TBI bretheren the simplicity of performing this modification. TBIs are usually a tad lean when stock and only get leaner with more modifications. To be sure you are tuning your new adjustable fuel pressure regulator for optimal performance at wide open throttle please see the paragraph about tuning at the end of the article.

OK lets get down to it!

Tools/Materials needed:

• T20 Torx bit (you can get away with an allen key but be carefull)

• Dremel with a cutoff disk (optional) You also MAY need an injector pod gasket though most may not.

Directions:

1. Disconnect negative battery cable

2. Remove aircleaner assembly

3. Remove gas cap to relieve system fuel pressure

4. Disconnect injectors and get the injector plugs out of the way aswell as the aircleaner stud (just turn it to face away from the injector pod)

5. Remove the Eight (8) Torx screws on the top of the injector pod. Take note of the positioning of the 3 longer screws.

6. With the screws removed from the top of the injector pod lift away the "roof" of the injector pod. Some fuel will leak out and be very carefull with the gasket so it does not tear or any debris fall into the path of fuel. The fuel pressure regulator is attached to it. It is the gold iridite "cup" looking object.

   Take note of the tab sticking out of the fuel pressure regulator cup. This represents the range of adjustment. The higher the tab is the more compressed the spring is equalling more fuel pressure. You’ll see what I mean later. GM seems to have no set fuel pressure as those who have performed this mod have all had varying fuel pressure settings from the factory.

7. Now you will have to dissasemble the fuel pressure regulator. There are four torx screws holding the cup to the injector pod "roof". Slowly and evenly loosen the screws while maintaining firm pressure on the cup because it holds a spring under some tension. remove screws evenly while maintaining pressure. Once all 4 screws are removed carefully lift away cup. the spring will release tension and you may set it aside along with the injector pod roof.

8. Take note of the fuel pressure regulators function. A small platform with a tab that sticks out the side of the cup rides on a threaded shaft. The higher the platform in the cup the more compressed the spring and the more fuel pressure is acheived.

9. Now to make that threaded shaft movable and furthermore, adjustable easily. You will have noticed the shaft does not move. Flip the cup over and take note of the pressed in cap in the hole on the bottom of the cup. This must be drilled out. Its pressed in there quite well, and is not easy just to pull out. I and others have had to completely drill out the cap.

   Be carefull so as to not exert too much pressure as it is possible to knock out the metal peice that is pressed into the cup on the bottom in which the cap sits

10. Now that you have drilled out the cap you will find that the screw and platform inside the cup are not only movable but removable from the cup. By turning the screw counter clockwise you raise the platform thus raising fuel pressure. You can raise the platform to a higher pressure and put it back together at this point but that takes away some of the adjustability to it.

11. Now if you have a dremel with a cutoff disk this is much easier though you might be able to accomplish this with a hacksaw. Cut a slot in the head of the screw so that a small flathead screwdriver can turn the screw.

12. Reassemble with a slightly higher fuel pressure setting. This time turn the cup around so that the tab does not face inwards and is not visible but faced out and is visible so that you can view the amount that the platform is raised. If you dont understand what I mean, just skip that.

13. Put injector pod "roof" back on top of injector pod. Be sure to snug down all screws to prevent leaks of fuel. REconnect Injectors, Put gas cap back on and reconnect negative battery cable.

14. Start car with aircleaner assembly removed from car and watch for leaks from the top of the injector pod. No leaks? great! If you have a leak be sure you tightened the screws. You might need a new gasket. Most autoparts stores sell gasket material to make one or you can buy one from GM. You might also be able to find a gasoline compatible silicon sealer. BE CAREFULL THOUGH you CAN clog your injectors.

15. Put aircleaner back on and refer to TUNING WITH YOUR O2 SENSOR & DIGITAL VOLT METER in the tech section to be sure you have the right pressure! To re-adjust pressure its going to take you to remove the 8 screws on the injector pod roof again and just use a small screwdriver counter clockwise in the little slot you made to raise fuel pressure and clockwise to decrease it.

This article is for educational purposes only. Do not think about attempting unless you feel confident with your mechanical abilities and know the basics of your TBI unit.

Pablo Morales
Olbap@Bellsouth.net